Acetaldehyde is an important precursor for the industrial production of high value chemicals such as pyridine derivatives, pentaerythritol, crotanaldehyde, acetic acid and vinyl acetate. Although acetaldehyde can be produced on an industrial scale from various routes such as oxidation of acetylene or ethylene via the Wacker process, hydration of acetylene, and vapour phase partial oxidation of butane, these processes all utilize an unstable or toxic starting material, often under high pressure, making them dangerous and costly for large-scale acetaldehyde production.
An alternative starting material for the production of acetaldehyde is ethanol. Ethanol is an attractive source for production of, high value chemicals because it can be produced economically and with low environmental impact via fermentation processes from renewable sources such as biomass feed stocks like corn, sugarcane and cellulose. In particular, second generation feed stocks such as lignocelluloses, wood chips, crop residues and tall grasses do not compete, with plant-based sources of food, making them cost-effective alternatives for renewable production of ethanol. Production of high value chemicals from ethanol is therefore currently attracting considerable interest because of the volatile prices of fossil fuel and concerns for the environment.
Reactions for converting ethanol to acetaldehyde include selective oxidation of ethanol (Eq.(1)) and oxidative dehydrogenation (Eq.(2)).CH3CH2OH+½O2→CH3CHO+H2O ΔH298=242 kJ/mol  Eq.(1)2CH3CH2OH+½O2→2CH3CHO+H2O+H2  Eq.(2)
However, the high temperature conditions required for the reactions described by Eq.(1) and Eq.(2) result in the production of significant amounts of carbon oxide by-products, described, for example, by Eq.(3), Eq.(4) and Eq.(5).CH3CH2OH(g)+H2O(g)→2CO(g)+4H2(g) ΔH298=256 kJ mol  Eq.(3)CH3CH2OH(g)+½O2→2CO(g)+2H2(g) ΔH298=14 kJ/mol  Eq.(4)CH3CH2OH(g)+½O2(g)+2H2O(g)→2CO2(g)+5H2(g) ΔH298=14 kJ/mol   Eq. (5)
The efficiency and selectivity of these reactions may be improved by the use of catalysts. However, catalysts for this reaction are known to be easily deactivated, require high reaction temperatures above 300° C. and have tendencies to produce various by-products which may decrease the yield and efficiency of the reaction. In general, even in the presence of catalysts, routes to convert ethanol to acetaldehyde are limited by selectivity, and conversion rates of greater than 80% are known to result in the formation, of mainly carbon oxide by-products. Above 0.200° C., the conversion selectivity to acetaldehyde decreases as the reaction temperature increases. These draw-backs make the conversion of ethanol to acetaldehyde on an industrial scale inefficient and costly.
Therefore, there is a need to provide an alternative catalyst to carry out the selective and efficient conversion of alcohols such as ethanol to aldehydes such as acetaldehyde. Further, there is a need for a method for selectively ad efficiently converting alcohols such as ethanol to aldehydes such as acetaldehyde.